1. Field of the Invention
The present invention relates to a communication method applicable to the orthogonal frequency division multiplex system (OFDM system) and a receiving apparatus for receiving a signal according to the communication method.
2. Description of the Related Art
For a communication method suitable for a mobile communication such as a wireless telephone system or the like, a multicarrier communication method called Orthogonal Frequency Division Multiplexing (OFDM system) has been proposed. This system is such that a plurality of subcarriers are arranged at a predetermined frequency interval within one transmission band and data is scattered over the respective subcarriers to modulate them for transmission. In this case, on a transmitting side, transmitting data in the form of a time sequence is orthogonal-transformed to a multicarrier signal at a predetermined frequency interval by a fast Fourier transform or the like. In this case, on a transmitting side, transmitting data in the form of a time sequence is orthogonal transformed to a multicarrier signal at a predetermined frequency interval by the inverse fast Fourier transform or the like. On a receiving side, a received multicarrier signal is subjected to the inverse transform to that in transmission for obtaining received data.
The transmitted signal according to the OFDM system has an advantage in that even if there is a multipath a good transmission characteristic is ensured, so that it is particularly suitable for the mobile communication such as the wireless telephone system or the like.
In the meantime, when receiving such a multicarrier signal, it is required to perform a receiving process in synchronism with a frame period of the multicarrier signal transmitted. Hence it is necessary to detect the frame period of the received signal by any method. Generally, in order to detect the frame period, some frame synchronous signal (a specified pattern signal) contained in the transmitted signal is detected and then the frame period is detected with reference to that detection timing.
However, if such a frame synchronous signal is made to be transmitted, a space which is capable of transmitting data will be reduced by that extent, thereby causing a transmission capacity to be reduced.